1. Field of the Invention
The present invention relates to a thin-film magnetic head that utilizes the magnetoresistive element for reading the magnetic field intensity of a magnetic recording medium, for example, as a signal, and a method of manufacturing such a thin-film magnetic head. The invention also relates to a method of forming a patterned thin film for a thin-film magnetic head that comprises a base body and a thin-film magnetic head element formed on the base body.
2. Description of the Related Art
Increase in recording density has been demanded of magnetic disk drives along with a demand for higher capacity and smaller sizes. Further, performance improvements in thin-film magnetic heads have been demanded. Thin-film magnetic heads in widespread use include composite thin-film magnetic heads. A composite thin-film magnetic head is made of a layered structure including a write (recording) head having an induction-type electromagnetic transducer for writing and a read (reproducing) head having a magnetoresistive (MR) element for reading that detects a magnetic field through the use of the magnetoresistive effect.
Read heads that exhibit high sensitivity and produce high outputs have been required. In response to such demands, attention has been focused on tunnel magnetoresistive elements (that may be hereinafter called TMR elements) that detect a magnetic field through the use of the tunnel magnetoresistive effect.
A TMR element normally has a structure in which a lower magnetic layer, a tunnel barrier layer and an upper magnetic layer are stacked. Each of the lower magnetic layer and the upper magnetic layer includes a ferromagnetic substance. In general, the magnetic layer closer to the substrate is called the lower magnetic layer and the magnetic layer farther from the substrate is called the upper magnetic layer. Therefore, the terms xe2x80x98upperxe2x80x99 and xe2x80x98lowerxe2x80x99 of the upper and lower magnetic layers do not always correspond to the position in the arrangement of an actual TMR element.
The tunnel barrier layer is a layer made of a thin nonmagnetic insulating film through which electrons are capable of passing while maintaining spins thereof by means of the tunnel effect, that is, through which a tunnel current is allowed to pass. The tunnel magnetoresistive effect is a phenomenon in which, when a current is fed to a pair of magnetic layers sandwiching the tunnel barrier layer, a tunnel current passing through the tunnel barrier layer changes, depending on the relative angle between magnetizations of the two magnetic layers. If the relative angle between magnetizations of the magnetic layers is small, the tunneling rate is high. As a result, the resistance to the current passing across the magnetic layers is reduced. If the relative angle between magnetizations of the magnetic layers is large, the tunneling rate is low. The resistance to the current passing across the magnetic layers is therefore increased.
With regard to the structure of a thin-film magnetic head incorporating a TMR element, if the tunnel barrier layer made up of a thin insulating layer is exposed in the medium facing surface that faces a recording medium, a short circuit may occur between the two magnetic layers opposed to each other with the tunnel barrier layer in between, during or after lapping of the medium facing surface. Such a structure is therefore not preferred.
To respond to such a problem, U.S. patent application Ser. No. 09/517,580, for instance, proposes a thin-film magnetic head having a structure in which a part where the lower magnetic layer, the tunnel barrier layer and the upper magnetic layer overlap (hereinafter called the tunnel joint) retreats from the medium facing surface, and a soft magnetic layer is provided for introducing a signal magnetic flux to the tunnel joint. The soft magnetic layer extends from the medium facing surface to the point in which the tunnel joint is located. In the present application this soft magnetic layer is called a front flux guide (FFG) and the thin-film magnetic head having the above-described structure is called an FFG-type TMR head. FFG may also serve as the lower or upper magnetic layer. In the FFG-type TMR head, when the medium facing surface is lapped to control the distance between the medium facing surface and the TMR element, the TMR element will never be lapped. Therefore, the FFG-type TMR head has a feature that the medium facing surface of the head is defined by mechanical lapping without creating a short circuit between the two magnetic layers.
Reference is now made to FIG. 25A to FIG. 31A and FIG. 25B to FIG. 31B to describe an example of a method of manufacturing the FFG-type TMR head. FIG. 25A to FIG. 31A and FIG. 25B to FIG. 31B illustrate the steps of the method. FIG. 25A to FIG. 31A show the integrated surfaces (on top face), whereas FIG. 25B to FIG. 31B show the cross sections on the position that corresponds to line 25Bxe2x80x9425B in FIG. 25A.
In this method, as shown in FIG. 25A and FIG. 25B, a lower electrode layer 102, a lower metallic layer 103, a lower ferromagnetic layer 104, a tunnel barrier layer 105, an upper ferromagnetic layer 106, a pinning layer 107 and a capping layer 108 are stacked one by one on a substrate that is not illustrated. Here, the pinning layer 107 is provided for fixing the magnetizing direction of the upper ferromagnetic layer 106 in the direction in which the magnetic field is detected. The capping layer 108 is provided for preventing deterioration of properties and oxidization of the surface of the pinning layer 107. A multi-layer film including the lower ferromagnetic layer 104, the tunnel barrier layer 105 and the upper ferromagnetic layer 106 is hereinafter called a TMR multi-layer film.
Next, a resist mask 109 used for patterning the TMR multi-layer film is formed by photolithography on the capping layer 108. After that, the capping layer 108, the pinning layer 107, the upper ferromagnetic layer 106, the tunnel barrier layer 105 and the lower ferromagnetic layer 104 are selectively etched through ion milling, for example, using the resist mask 109 to pattern the TMR multi-layer film as shown in FIG. 26A and FIG. 26B. The resist mask 109 is then removed.
Next, as shown in FIG. 27A and FIG. 27B, resist masks 110 are formed by photolithography on the lower metallic layer 103 and the capping layer 108, to cover regions except where hard magnetic layers are to be formed. Subsequently, the capping layer 108, the pinning layer 107, the upper ferromagnetic layer 106, the tunnel barrier layer 105 and the lower ferromagnetic layer 104 are selectively etched by ion milling, for example, using the resist masks 110.
Next, as shown in FIG. 28A and FIG. 28B, hard magnetic layers 111 are formed on regions of the lower metallic layer 103 that are not covered with the resist masks 110. The hard magnetic layers 111 are for applying a bias magnetic field to the tunnel joint. The resist masks 110 are then lifted off.
Next, as shown in FIG. 29A and FIG. 29B, a resist mask 112 is formed on the capping layer 108 by photolithography. This resist mask is for defining the shape of the tunnel joint.
Next, as shown in FIG. 30A and FIG. 30B, at least the capping layer 108, the pinning layer 107 and the upper ferromagnetic layer 106 are selectively etched using the resist mask 112, for example through ion milling, to define the shape of the tunnel joint. Here, a position at which the etching is to be stopped is set at a predetermined position between the top surface of the tunnel barrier layer 105 and a position located partway through the lower ferromagnetic layer 104 in its thickness direction. Next, an insulation layer 113 is formed over the surface and the resist mask 112 is then lifted off.
Next, as shown in FIG. 31A and FIG. 31B, an upper electrode layer 114 is formed on the capping layer 108 and on the insulation layer 113. Thus, a TMR element component and its periphery in an FFG-type TMR head are formed. In this FFG-type TMR head, the lower ferromagnetic layer 104 is T-shaped with a portion extending from the tunnel joint towards the medium facing surface (or lower in FIG. 25A to FIG. 31A) and two other portions extending from the tunnel joint towards both sides in a direction parallel to the medium facing surface. This lower ferromagnetic layer 104 serves as FFG.
In general, on a single wafer (substrate), a large number of parts that will be heads (hereinafter called head parts) are formed and, an aggregate of the head parts is cut into individual heads. In the process of cutting the aggregate of head parts into final heads, the medium facing surface of each head is defined by lapping. Through this lapping process, the lower ferromagnetic layer 104, serving as FFG, is exposed in the medium facing surface and the distance between the medium facing surface and the tunnel joint is controlled.
A flying-type thin-film magnetic head for magnetic disk drives is in general in the shape of a slider with a thin-film magnetic head element formed at its rear end. Here, the thin-film magnetic head element refers to the part incorporating an MR element or an induction-type electromagnetic transducer and electromagnetically functioning as a magnetic head. A slider has rails on the side of the medium facing surface and is designed to slightly fly over a recording medium by means of an airflow generated by the rotation of the medium. A medium facing surface of a flying-type thin-film magnetic head is also called an air bearing surface.
In the process of manufacturing an FFG-type TMR head as described above, when at least the capping layer 108, the pinning layer 107 and the upper ferromagnetic layer 106 are selectively etched to define the shape of the tunnel joint as shown in FIG. 30A and FIG. 30B, it is necessary to achieve a highly precise control of a position at which etching is to be stopped, so as to suppress variations in properties of heads.
For performing etching by ion milling up to a specific layer in the multi-layer film or to a predetermined position located partway through a specific layer in the multi-layer film, the position at which the etching is to be stopped can be controlled by performing a measurement for identifying scattered elements arising from the ion milling, using Secondary Ion Mass Spectrometry (SIMS), for example. In this case, the measurement for identifying the scattered elements is performed concurrently with ion milling. The material of a film being etched and the depth of the etching in the film are judged from the measurement results on a real-time basis, to thereby control the position at which the etching is to be stopped.
Published Unexamined Japanese Patent Application KOKAI) Heisei 11-274600 (1999) discloses a method of controlling a position at which etching is to be stopped, by detecting the intensity of the light from the elements in a layer being etched during ion milling to judge the material of the layer and the depth of the etching in the layer on a real-time basis.
However, in the method of manufacturing the FFG-type TMR head as shown in FIG. 25A to FIG. 31A and FIG. 25B to FIG. 31B, the finely-patterned TMR multi-layer film is etched using the resist mask 112, as shown in FIG. 29A to FIG. 29B, when the shape of the tunnel joint is defined. This makes the region etched for defining the shape of the tunnel joint extremely small in area. It means that there is a limited amount of scattered substances involved in the process of the etching for defining the shape of the tunnel joint, so that it is difficult to make a precise measurement for identifying the scattered elements as mentioned above. Consequently, it is difficult to accurately control a position at which the etching is to be stopped.
A possible solution to the foregoing problem is making a dummy region on an integrated surface of a wafer separately from the head parts, to use the dummy region for measurement for identifying elements scattered during etching. From the viewpoint of efficiency in manufacturing heads, however, it is preferable to increase the number of heads obtainable from one wafer. To achieve this, it is necessary to increase the density of head parts on a wafer. Hence, it is unfavorable in the respect of efficiency in manufacturing heads to make a dummy region separately from the head parts on the integrated surface of a wafer, as it leads to a lower density of the head parts on the wafer.
Another conceivable remedy is to use a dummy wafer prepared with films of the same composition as that of the films for forming the head, separate from the wafer having the actual films for forming the head thereon. The dummy wafer is used to perform measurements by SIMS, for example, to learn the relationship between the duration of etching for defining the shape of the tunnel joint and the type of scattered elements and their amount, beforehand. Then, based on the relationship, a required duration of the etching for defining the shape of the tunnel joint is calculated. However, this method lowers the efficiency of head production, as it requires calculation of the relationship between the duration of etching and the type and the amount of scattered substances every time the composition of the films for forming the head is changed. Moreover, due to variations in the status of films between wafers, the position at which the etching is to be stopped cannot always be accurately controlled for each wafer, because this method controls the duration of the etching on the actual films for forming the head based on the measurement results obtained through etching the films on the dummy wafer. Accordingly, this method cannot sufficiently suppress variations in properties of heads.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing same, and a method of forming a patterned thin-film for a thin-film magnetic head, which make it possible to suppress variations in properties of heads arising from variations in positions at which etching is stopped, without lowering the production efficiency.
A method of manufacturing a thin-film magnetic head of the invention is provided for manufacturing a thin-film magnetic head having a magnetoresistive element, the method comprising the steps of:
forming a film for the magnetoresistive element, which is used for forming the magnetoresistive element, and a dummy film having a composition the same as that of the film for the magnetoresistive element and not used for forming the magnetoresistive element, into predetermined shapes respectively, on a base on which the magnetoresistive element is to be formed, within a region in which one thin-film magnetic head is to be formed;
in order to form the magnetoresistive element by etching a part of the film for the magnetoresistive element, etching a part of the film for the magnetoresistive element in its thickness direction in a specific region within the film, and a part of the dummy film in its thickness direction at the same time; and
controlling a position at which the etching is to be stopped, by performing, in the step of etching, a measurement for identifying elements scattered from the film for the magnetoresistive element and from the dummy film due to the etching, so as to perform the control based on results thereof.
According to the method of manufacturing a thin-film magnetic head of the invention, the film for the magnetoresistive element and the dummy film are etched at the same time in the step of the etching. Further, in the step of controlling a position at which the etching is to be stopped, a measurement is performed for identifying elements that are scattered from the film for the magnetoresistive element and from the dummy film due to the etching. Therefore, the invention allows to perform the measurement with high precision and consequently makes it possible to control a position at which the etching is to be stopped with high precision.
In the method of manufacturing a thin-film magnetic head of the invention, each of the film for the magnetoresistive element and the dummy film may include a first magnetic layer, a tunnel barrier layer and a second magnetic layer that are stacked in this order on the base. In this case, the position at which the etching is to be stopped may be any of: a boundary between the second magnetic layer and the tunnel barrier layer; a position located partway through the tunnel barrier layer in its thickness direction; a boundary between the tunnel barrier layer and the first magnetic layer; and a position located partway through the first magnetic layer in its thickness direction.
The method of manufacturing a thin-film magnetic head of the invention may further comprise the step of forming a metallic layer that serves as the base on which the film for the magnetoresistive element and the dummy film are formed. In this case, the metallic layer may be formed of a non-magnetic metal.
In the method of manufacturing a thin-film magnetic head of the invention, the dummy film may be formed at a position where it is hidden from an integrated surface by a patterned thin film formed after the dummy film has been formed.
In the method of manufacturing a thin-film magnetic head of the invention, the dummy film may have a shape that represents a symbol for identifying each individual thin-film magnetic head.
In the method of manufacturing a thin-film magnetic head of the invention, a region in which the dummy film is formed may have an area that falls within a range of 0.05 to 30 percent of the area of the region in which one thin-film magnetic head is to be formed.
In the method of manufacturing a thin-film magnetic head of the invention, a region in which the dummy film is formed may have an area that falls within a range of 0.1 to 20 percent of the area of the region in which one thin-film magnetic head is to be formed.
A thin-film magnetic head of the invention has a magnetoresistive element and a dummy component that are formed on a base. The magnetoresistive element is formed by etching a part of a film for the magnetoresistive element, the film having a specific shape and being used for forming the magnetoresistive element, in its thickness direction in a specific region within the film. The dummy component is formed by etching a part of a dummy film in its thickness direction, the dummy film having a composition the same as that of the film for the magnetoresistive element and not being used for forming the magnetoresistive element.
The thin-film magnetic head of the invention has the dummy component formed by etching a part of the dummy film in its thickness direction. When forming the magnetoresistive element by etching a part of the film for the magnetoresistive element so as to manufacture the thin-film magnetic head of the invention, it is possible to etch the film for the magnetoresistive element and the dummy film at the same time. Therefore, according to the invention, it is possible to perform the measurement for identifying elements scattered from the film for the magnetoresistive element and from the dummy film due to the etching with high precision, and thereby to control, with high precision, a position at which the etching is to be stopped.
In the thin-film magnetic head of the invention, the magnetoresistive element may include a first magnetic layer, a tunnel barrier layer and a second magnetic layer that are stacked in this order on the base. In this case, one of surfaces of the dummy component farther from the base may be located at: a position corresponding to a boundary between the second magnetic layer and the tunnel layer of the magnetoresistive element in a direction of thickness of the magnetoresistive element; a position corresponding to a position located partway through the tunnel barrier layer of the magnetoresistive element in a direction of thickness of the magnetoresistive element; a position corresponding to a boundary between the tunnel barrier layer and the first magnetic layer of the magnetoresistive element in a direction of thickness of the magnetoresistive element; or a position corresponding to a position located partway through the first magnetic layer of the magnetoresistive element in a direction of thickness of the magnetoresistive element.
The thin-film magnetic head of the invention may further have a metallic layer that serves as the base on which the magnetoresistive element and the dummy component are formed. In this case, the metallic layer may be formed of a non-magnetic metal.
In the thin-film magnetic head of the invention, the dummy component may be formed at a position where it is hidden from an integrated surface by a patterned thin film formed after the dummy component has been formed.
In the thin-film magnetic head of the invention, the dummy component may have a shape that represents a symbol for identifying each individual thin-film magnetic head.
In the thin-film magnetic head of the invention, a region in which the dummy component is provided may have an area that falls within a range of 0.05 to 30 percent of the area of a surface of the thin-film magnetic head on which the magnetoresistive element and the dummy component are provided.
In the thin-film magnetic head of the invention, a region in which the dummy component is provided may have an area that falls within a range of 0.1 to 20 percent of the area of a surface of the thin-film magnetic head on which the magnetoresistive element and the dummy component are provided.
A method of forming a patterned thin film according to the invention is provided for forming a patterned thin film for a thin-film magnetic head that includes a base body and a thin-film magnetic head element formed on the base body. The patterned thin film is included in the thin-film magnetic head element. The thin-film magnetic head element is formed by etching a part of a film to be etched having a specific shape, in a direction of thickness of the film to be etched in a specific region within the film to be etched. The method of the invention includes the steps of:
forming the film to be etched and a dummy film that has a composition the same as that of the film to be etched and is not used for forming the patterned thin film, into predetermined shapes respectively, on a base on which the patterned thin film is to be formed, within a region in which one thin-film magnetic head is to be formed;
in order to form the patterned thin film by etching a part of the film to be etched, etching a part of the film to be etched in its thickness direction in a specific region within the film, and a part of the dummy film in its thickness direction at the same time; and
controlling a position at which the etching is to be stopped, by performing, in the step of etching, a measurement for identifying elements scattered from the film to be etched and from the dummy film due to the etching, so as to perform the control based on results thereof.
According to the method of forming a patterned thin film of the invention, the film to be etched and the dummy film are etched at the same time in the step of etching. Further, in the step of controlling a position at which the etching is to be stopped, a measurement is performed for identifying elements that are scattered from the film to be etched and from the dummy film due to the etching. Therefore, the invention allows to perform the measurement with high precision and consequently makes it possible to control a position at which the etching is to be stopped with high precision.
Other and further objects, features and advantages of the invention will appear more fully from the following description.